The present invention relates to the cleaning and recovery of metal-containing residues such as tantalum from the surface of processing chamber components.
In the processing of substrates, such as semiconductor wafers and displays, a substrate is placed in a process chamber and exposed to an energized gas to deposit or etch material on the substrate. During such processing, process residues are generated and deposited on internal surfaces in the chamber. For example, in sputter deposition processes, material sputtered from a target for deposition on a substrate also deposits on other component surfaces in the chamber, such as on deposition rings, cover ring, shadow rings, inner shield, upper shield, wall liners, and focus rings. In subsequent process cycles, the deposited process residues can “flake off” from the chamber component surfaces to fall upon and contaminate the substrate. Consequently, the deposited process residues are periodically cleaned from the chamber surfaces.
However, it is difficult to clean process deposits that contain metals such as tantalum from chamber components, especially when the components are made of metal-containing materials. When tantalum is sputter deposited onto the substrate, some of the sputtered tantalum deposits upon the adjacent chamber component surfaces. These tantalum process deposits are difficult to remove because cleaning solutions suitable for their removal are also frequently reactive with other metals, such as titanium, that are used to form chamber components. Cleaning of tantalum-containing materials from such surfaces can erode the components and require their frequent replacement. The erosion of metal surfaces can be especially problematic when cleaning textured metal surfaces, such as surfaces formed by a “Lavacoat™” process. These surfaces have crevices and pores in which tantalum-containing process residues get lodged, making it difficult to remove these residues with conventional cleaning process.
When conventional cleaning methods are used to clean tantalum, an amount of the tantalum-containing material generated in these process is not recovered. It is estimated that in many tantalum deposition processes, only about one-half of the sputtered tantalum material is deposited on the substrate, the rest being deposited on component surfaces within the chamber. Conventional cleaning methods frequently dispose of the used cleaning solutions along with the dissolved tantalum material. Thus, a large amount of tantalum material is wasted after it is cleaned off the chamber surfaces, resulting in an estimated loss of about 30,000 pounds of tantalum per year. The disposal of tantalum is environmentally undesirable and costly because high purity tantalum is expensive and fresh cleaning solution has to be acquired.
Thus, it is desirable to have a method of cleaning metal-containing deposits such as tantalum-containing deposits from surfaces of components without excessively eroding the surfaces. It is also desirable to reduce the waste of the tantalum materials cleaned off the chamber surfaces. It is further desirable to have a method of recovering cleaning solutions which are used to clean the tantalum-containing residues.